Biogas Slurry and Organo-Mineral Integration: Drivers of Arylsulfatase, Urease and FDA Enzyme Stimulation in Soil

Abstract

Sustaining productivity in intensive rice–wheat system requires strategies that enhance soil biological functioning alongside nutrient supply. A two-year field experiment (2022-2024) was held at ICAR-Indian Agricultural Research Institute (IARI), New Delhi, to evaluate the impact of integrated application of biogas slurry (BGS) and recommended dose of fertilizers (RDF) on soil enzymatic activities. Under randomised block design (RBD) investigation, six treatments, each containing different amounts of nitrogen doses supplied through BGS and RDF. Soil samples collected at the reproductive stage of wheat were analyzed for arylsulfatase, urease and fluorescein diacetate (FDA) hydrolase activities using standard procedures. Results indicated significant enhancement of all enzymes under integrated and sole BGS treatments compared to control and sole RDF. Arylsulfatase activity ranged from 35.31 to 73.98 µg PNP g⁻¹ h⁻¹ in 2023 and 37.75 to 81.92 µg PNP g⁻¹ h⁻¹ in 2024. Urease activity varied from 103.45 to 178.83 µg NH₄⁺-N g⁻¹ h⁻¹ in 2023 and 119.18 to 204.76 µg NH₄⁺-N g⁻¹ h⁻¹ in 2024. FDA activity ranged from 39.31 to 77.98 µg g⁻¹ soil h⁻¹ in 2023 and 43.75 to 87.92 µg g⁻¹ soil h⁻¹ in 2024. Enzymatic activities followed the trend: 100% BGS > 75% BGS + 25% RDF ≈ 50% BGS + 50% RDF > 25% BGS + 75% RDF > 100% RDF > control. Higher values in the second year suggest cumulative effects of organic amendments. The findings demonstrate that substituting mineral nitrogen with biogas slurry enhances soil enzymatic activity, nutrient mineralization and overall soil health, supporting sustainable intensification of rice–wheat cropping system.